Mil Tech — Climbing the Walls
Aug 02 2010
The Defense Advance Research Projects Agency (DARPA) continues its attention to wall-climbing projects, funding various initiatives that might help servicemembers scale vertical surfaces without ladders or ropes.
Using an adhesive bond similar to the adhering qualities of the Palm beetle, Cornell University researchers in Ithaca, N.Y., have developed a water-based, hand-sized device that can bear loads while it sticks to and releases from walls.
The device contains a triple-layer plate and 9-volt battery that produce enough surface tension to hold up 15 pounds per square inch of device. Researchers estimate a 225-pound servicemember could be supported by a 3-by-5-inch plate on the sole of a boot.
Paul H. Steen, lead researcher in Cornell’s Chemical and Biomolecular Engineering Department, says the device is known as SECAD (Switchable Electronically Controlled Adhesive Device).
“Surface tension can be demonstrated by two pieces of glass with water in between them adhering to each other, known as wetting phenomenon,” Steen says. “Our device uses surface tension, but it’s main advantage is that we can turn it on and off.”
The project goal is to produce an epoxy-strength adhesive that can be turned on or off in a fraction of a second.
Mark Cutkowski of the Department of Mechanical Engineering at Stanford University’s Center for Design Research in Palo Alto, Calif., subcontracts with Draper Laboratory to explore the use of dry adhesive materials for climbing applications. His group developed Stickybot, a robot with sticky feet that mimics the climbing action of geckos by using feet made with a synthetic elastomer, promoting a strong contact between the feet and a wall.
For efficient climbing, he notes, one must have direction adhesion, like a gecko, where it brushes against a surface and pulls in one direction to stick itself, and pulls in another direction to release itself without any effort.
Cutkowski says a 4-by-4-inch patch of synthetic adhesive could support about 30 pounds. The goal, he notes, is an application that can stick and unstick many times with no residue, and last many cycles, yet not expending much energy. The Stickybot, he says, must stick and unstick at least 120 times a minute in order to climb.
The challenges for humans to be able to walk on or climb walls, says Steen, is that such materials must work as well on dusty or wet surfaces as they do on smooth ones.
“While the Spiderman thing has a lot of appeal,” he notes, “it will be more than five years before you can go to a store and get gloves that will allow you to walk up walls.”
About the author: Alan M. Petrillo is a Tucson, Ariz., freelance writer who works in a wide variety of fields, writing for national and regional magazines and newspapers. He’s also the author of the mystery novel, Full Moon, and several books on historical military small arms
